Attached patch makes the dictproxy type public. Example:

$ ./python 
Python 3.3.0a1+ (default:059489cec7b9+, Mar 22 2012, 02:45:36) 
>>> d=dictproxy({1:2})
>>> d
dict_proxy({1: 2})
>>> d[1]
2
>>> d[1]=3
TypeError: 'dictproxy' object does not support item assignment
>>> del d[1]
TypeError: 'dictproxy' object doesn't support item deletion
>>> d.copy()
{1: 2}
>>> dir(d)
[..., '__getitem__', 'copy', 'get', 'items', 'keys', 'values']

The patch doesn't have any test or documentation yet.

See also the (now rejected) PEP 416 (frozendict).